We are continuing experiments on the synergy of immunologic injury to arteries and hyperlipidemia in the pathogenesis of serum sickness in the rabbit. We are studying the effect of dietary modification on the regression of athero-arteriosclerosis so induced. The role of atopic or IgE mediated allergy in producing changes in vascular permeability and the development of atherosclerosis is being studied. The relationship of immunologically and otherwise induced endothelial injury to the pathogenesis of arteriosclerosis is being evaluated. We are continuing investigations on contractile and relaxing proteins of the cardiovascular system with emphasis on regional differences in endothelium. Immunohistologic techniques for ultrastructural localization of contractile proteins are being developed. We are investigating the pathogenesis of glomerulonephritis and rheumatic heart disease induced experimentally by infection with group A streptococci. We are studying the relationship of maternal infection and fetal immunization with streptococci to the development of these sequelae.